ISO 21460:2007

Space data and information transfer systems — Proximity-1 space link protocol — Physical layer

ISO 21460:2007 defines the Proximity-1 space link protocol physical layer. It specifies the channel connection process, provision for frequency bands and assignments, hailing channel, polarization, modulation, data rates, and performance requirements. Currently, the physical layer only defines operations at UHF frequencies for the Mars environment. The coding layer is defined in ISO 21459. The data link layer is defined in ISO 22663. ISO 21460:2007 does not specify individual implementations or products; implementation of service interfaces within real systems; the methods or technologies required to perform the procedures; or the management activities required to configure and control the protocol. The scope and field of application are furthermore detailed in subclause 1.3 of the enclosed CCSDS publication.

Systèmes de transfert des informations et données spatiales — Protocole pour liaisons spatiales de proximité 1 — Couche physique

General Information

• Status: Withdrawn
• Publication Date: 09-Oct-2007
• Withdrawal Date: 09-Oct-2007
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Drafting Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 11-Aug-2015

Relations

• Revised: ISO 21460:2015 - Space data and information transfer systems — Proximity-1 space link protocol — Physical layer
• Effective Date: 02-Aug-2014
• Revises: ISO 21460:2006 - Space data and information transfer systems — Proximity-1 space link protocol — Physical layer
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21460
Second edition
2007-10-15


Space data and information transfer
systems — Proximity-1 space link
protocol — Physical layer
Systèmes de transfert des informations et données spatiales —
Protocole pour liaisons spatiales de proximité 1 — Couche physique




Reference number
ISO 21460:2007(E)
©
ISO 2007

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ISO 21460:2007(E)
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ISO 21460:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21460 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.
This second edition cancels and replaces the first edition (ISO 21460:2006), which has been technically
revised.
ISO 21460 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as
CCSDS 211.1-B-3, March 2006) and was adopted (without modifications except those stated in Clause 2 of
this International Standard) by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 13, Space data and information transfer systems.

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INTERNATIONAL STANDARD ISO 21460:2007(E)

Space data and information transfer systems — Proximity-1
space link protocol — Physical layer
1 Scope
This International Standard defines the Proximity-1 space link protocol physical layer. It specifies the channel
connection process, provision for frequency bands and assignments, hailing channel, polarization, modulation,
data rates, and performance requirements. Currently, the physical layer only defines operations at UHF
frequencies for the Mars environment. The coding layer is defined in ISO 21459. The data link layer is defined
in ISO 22663.
This International Standard does not specify
a) individual implementations or products;
b) implementation of service interfaces within real systems;
c) the methods or technologies required to perform the procedures; or
d) the management activities required to configure and control the protocol.
The scope and field of application are furthermore detailed in subclause 1.3 of the enclosed CCSDS
publication.
2 Requirements
Requirements are the technical recommendations made in the following publication (reproduced on the
following pages), which is adopted as an International Standard:
CCSDS 211.1-B-3, March 2006, Proximity-1 space link protocol — Physical layer.
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 211.1-B-3.
Pages i to v
This part is information which is relevant to the CCSDS publication only.
Page 1-5
Add the following information to the reference indicated:
[2] Document CCSDS 131.0-B-1, September 2003, is equivalent to ISO 22641:2005.
[3] Document CCSDS 211.2-B-1, April 2003, is equivalent to ISO 21459:2006.
[4] Document CCSDS 211.0-B-3, May 2004, is equivalent to ISO 22663:2006.
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ISO 21460:2007(E)
3 Revision of publication CCSDS 211.1-B-3
It has been agreed with the Consultative Committee for Space Data Systems that Subcommittee
ISO/TC 20/SC 13 will be consulted in the event of any revision or amendment of publication CCSDS 211.1-B-3.
To this end, NASA will act as a liaison body between CCSDS and ISO.
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ISO 21460:2007(E)


Recommendation for Space Data System Standards
PROXIMITY-1 SPACE LINK PROTOCOL—
PHYSICAL LAYER
RECOMMENDED STANDARD
CCSDS 211.1-B-3
BLUE BOOK
March 2006

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ISO 21460:2007(E)
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
AUTHORITY



Issue: Recommended Standard, Issue 3
Date: March 2006
Location: Washington, DC, USA

This document has been approved for publication by the Management Council of the
Consultative Committee for Space Data Systems (CCSDS) and represents the consensus
technical agreement of the participating CCSDS Member Agencies. The procedure for
review and authorization of CCSDS Recommendations is detailed in the Procedures Manual
for the Consultative Committee for Space Data Systems, and the record of Agency
participation in the authorization of this document can be obtained from the CCSDS
Secretariat at the address below.


This document is published and maintained by:

CCSDS Secretariat
Office of Space Communication (Code M-3)
National Aeronautics and Space Administration
Washington, DC 20546, USA
CCSDS 211.1-B-3 Page i March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of its members. The Committee meets periodically to address
data systems problems that are common to all participants, and to formulate sound technical
solutions to these problems. Inasmuch as participation in the CCSDS is completely voluntary,
the results of Committee actions are termed Recommended Standards and are not
considered binding on any Agency.
This Recommended Standard is issued by, and represents the consensus of, the CCSDS
members. Endorsement of this Recommendation is entirely voluntary. Endorsement,
however, indicates the following understandings:
o Whenever a member establishes a CCSDS-related standard, this standard will be in
accord with the relevant Recommended Standard. Establishing such a standard
does not preclude other provisions which a member may develop.
o Whenever a member establishes a CCSDS-related standard, that member will
provide other CCSDS members with the following information:
-- The standard itself.
-- The anticipated date of initial operational capability.
-- The anticipated duration of operational service.
o Specific service arrangements shall be made via memoranda of agreement. Neither
this Recommended Standard nor any ensuing standard is a substitute for a
memorandum of agreement.
No later than five years from its date of issuance, this Recommended Standard will be
reviewed by the CCSDS to determine whether it should: (1) remain in effect without change;
(2) be changed to reflect the impact of new technologies, new requirements, or new
directions; or (3) be retired or canceled.
In those instances when a new version of a Recommended Standard is issued, existing
CCSDS-related member standards and implementations are not negated or deemed to be non-
CCSDS compatible. It is the responsibility of each member to determine when such
standards or implementations are to be modified. Each member is, however, strongly
encouraged to direct planning for its new standards and implementations towards the later
version of the Recommended Standard.
CCSDS 211.1-B-3 Page ii March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
FOREWORD
Through the process of normal evolution, it is expected that expansion, deletion, or
modification of this document may occur. This Recommendation is therefore subject to
CCSDS document management and change control procedures which are defined in the
Procedures Manual for the Consultative Committee for Space Data Systems. Current
versions of CCSDS documents are maintained at the CCSDS Web site:
http://www.ccsds.org/
Questions relating to the contents or status of this document should be addressed to the
CCSDS Secretariat at the address indicated on page i.
CCSDS 211.1-B-3 Page iii March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
At time of publication, the active Member and Observer Agencies of the CCSDS were:

Member Agencies

– Agenzia Spaziale Italiana (ASI)/Italy.
– British National Space Centre (BNSC)/United Kingdom.
– Canadian Space Agency (CSA)/Canada.
– Centre National d’Etudes Spatiales (CNES)/France.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Federal Space Agency (Roskosmos)/Russian Federation.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– Japan Aerospace Exploration Agency (JAXA)/Japan.
– National Aeronautics and Space Administration (NASA)/USA.

Observer Agencies

– Austrian Space Agency (ASA)/Austria.
– Belgian Federal Science Policy Office (BFSPO)/Belgium.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– Centro Tecnico Aeroespacial (CTA)/Brazil.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– Danish Space Research Institute (DSRI)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– Korea Aerospace Research Institute (KARI)/Korea.
– MIKOMTEK: CSIR (CSIR)/Republic of South Africa.
– Ministry of Communications (MOC)/Israel.
– National Institute of Information and Communications Technology (NICT)/Japan.
– National Oceanic & Atmospheric Administration (NOAA)/USA.
– National Space Organization (NSPO)/Taipei.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 211.1-B-3 EC1 Page iv December 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
DOCUMENT CONTROL

Document Title and Issue Date Status

CCSDS Proximity-1 Space Link Protocol October Superseded
211.0-B-1 2002

CCSDS Proximity-1 Space Link Protocol— May Superseded
211.1-B-2 Physical Layer 2004

CCSDS Proximity-1 Space Link Protocol— March Current issue:
211.1-B-3 Physical Layer, Recommended 2006 – adds requirements for
Standard, Issue 3 data rate offset and
short- and long-term
rate stability.

CCSDS Proximity-1 Space Link Protocol— December Editorial update:
211.1-B-3 Physical Layer, Recommended 2006 – Updates Agencies in
EC1 Standard, Issue 3, Editorial Foreword; corrects page
Corrigendum 1 numbering on page 2-4;
removes extraneous
material and corrects
paragraph numbering on
pages 3-9 and 3-10.
NOTES
1 Changes from the previous issue are flagged with change bars in the inside margin.
2 This document contains the Physical layer specification originally published as part of
CCSDS 211.0-B-1, Proximity-1 Space Link Protocol.
CCSDS 211.1-B-3 EC1 Page v December 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
CONTENTS
Section Page
1 INTRODUCTION. 1-1

1.1 PURPOSE.1-1
1.2 SCOPE.1-1
1.3 APPLICABILITY.1-1
1.4 RATIONALE.1-2
1.5 CONVENTIONS AND DEFINITIONS. 1-2
1.6 REFERENCES.1-5

2 OVERVIEW. 2-1

3 GENERAL REQUIREMENTS FOR THE PHYSICAL LAYER . 3-1

3.1 APPLICABILITY.3-1
3.2 FUNCTIONAL REQUIREMENTS.3-1
3.3 IDLE DATA.3-4
3.4 CONTROLLED COMMUNICATIONS CHANNEL PROPERTIES . 3-5
3.5 PERFORMANCE REQUIREMENTS.3-10

ANNEX A DIRECTIVES AFFECTING THE PROXIMITY-1
PHYSICAL LAYER (Normative) . A-1
Figure
1-1 Bit Numbering Convention. 1-5
2-1 Proximity-1 Layered Protocol Model . 2-1
3-1 Oscillator Phase Noise. 3-11
3-2 Discrete Lines Template for the Transmitter (Normalized Power in dBc vs.
Normalized Frequency: (f-f )/A). 3-12
c

Table
3-1 Categories of Radio Equipment Contained on Proximity-1 Link Elements. 3-1
3-2 Proximity-1 Channel Assignments 0 through 7 (Frequencies in MHz). 3-8


CCSDS 211.1-B-3 EC1 Page vi December 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
1 INTRODUCTION
1.1 PURPOSE
The purpose of this document is to provide a Recommendation for Space Data System
Standards in the area of Proximity space links. Proximity space links are defined to be short-
range, bi-directional, fixed or mobile radio links, generally used to communicate among
probes, landers, rovers, orbiting constellations, and orbiting relays. These links are
characterized by short time delays, moderate (not weak) signals, and short, independent
sessions.
1.2 SCOPE
This Recommendation defines the Proximity-1 Space Link Protocol Physical Layer. The
specification for the channel connection process, provision for frequency bands and
assignments, hailing channel, polarization, modulation, data rates, and performance
requirements are defined in this document. Currently, the Physical Layer only defines
operations at UHF frequencies for the Mars environment. The Coding layer is defined in the
separate CCSDS recommendation entitled, Proximity-1 Space Link Protocol—Coding and
Synchronization Sublayer; see reference [3]. The Data Link layer is defined in the separate
CCSDS recommendation entitled, Proximity-1 Space Link Protocol—Data Link Layer; see
reference [4]. This Recommendation does not specify a) individual implementations or
products, b) implementation of service interfaces within real systems, c) the methods or
technologies required to perform the procedures, or d) the management activities required to
configure and control the protocol.
1.3 APPLICABILITY
This Recommendation applies to the creation of Agency standards and to future data
communications over space links between CCSDS Agencies in cross-support situations. It
applies also to internal Agency links where no cross-support is required. It includes
specification of the services and protocols for inter-Agency cross support. It is neither a
specification of, nor a design for, systems that may be implemented for existing or future
missions.
The Recommendation specified in this document is to be invoked through the normal
standards programs of each CCSDS Agency and is applicable to those missions for which
cross support based on capabilities described in this Recommendation is anticipated. Where
mandatory capabilities are clearly indicated in sections of the Recommendation, they must be
implemented when this document is used as a basis for cross support. Where options are
allowed or implied, implementation of these options is subject to specific bilateral cross
support agreements between the Agencies involved.
CCSDS 211.1-B-3 Page 1-1 March 2006
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ISO 21460:2007(E) 1
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
1.4 RATIONALE
The CCSDS believes it is important to document the rationale underlying the
recommendations chosen, so that future evaluations of proposed changes or improvements
will not lose sight of previous decisions. Concept and rationale behind the decisions that
formed the basis for Proximity-1 will be documented in the CCSDS Proximity-1 Space Link
Green Book, which is under development.
1.5 CONVENTIONS AND DEFINITIONS
1.5.1 DEFINITIONS
1.5.1.1 Definitions from the Open Systems Interconnection (OSI) Basic Reference
Model
This Recommendation makes use of a number of terms defined in reference [1]. The use of
those terms in this Recommendation shall be understood in a generic sense, i.e., in the sense
that those terms are generally applicable to any of a variety of technologies that provide for
the exchange of information between real systems. Those terms are as follows:
a) connection;
b) Data Link layer;
c) entity;
d) physical layer;
e) protocol control information;
f) Protocol Data Unit (PDU);
g) real system;
h) segmenting;
i) service;
j) Service Access Point (SAP);
k) SAP address;
l) Service Data Unit (SDU).
1.5.1.2 Terms Defined in This Recommendation
For the purposes of this Recommendation, the following definitions also apply. Many other
terms that pertain to specific items are defined in the appropriate sections.
CCSDS 211.1-B-3 Page 1-2 March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
asynchronous channel: a data channel where the symbol data are modulated onto the
channel only for the period of the message. The message must be preceded by an
acquisition sequence to achieve symbol synchronization. Bit synchronization must be
reacquired on every message. A hailing channel is an example of an asynchronous
channel.
asynchronous data link: a data link consisting of a sequence of variable-length Proximity
Link Transmission Units (PLTUs), which are not necessarily concatenated. Two
types of asynchronous data links are:
1) Asynchronous Data Link over an Asynchronous Channel
Hailing provides an example of an asynchronous data link over an asynchronous
channel. An important issue is resynchronization between successive hails. Idle
is provided for the reacquisition process.
2) Asynchronous Data Link over a Synchronous Channel
Data service provides an example of an asynchronous data link over a
synchronous channel. Once the link is established via hailing, communication
transitions to a synchronous channel and maintains the link in this configuration
until the session is interrupted or ends. If the physical layer does not receive data
from the data link layer, it provides idle to maintain a synchronous channel.
caller and responder: A caller transceiver is the initiator of the link establishment process
and manager of negotiation (if required) of the session. A responder transceiver
typically receives link establishment parameters from the caller. The caller initiates
communication between itself and a responder on a pre-arranged communications
channel with predefined controlling parameters. As necessary, the caller and
responder may negotiate the controlling parameters for the session (at some level
between fully controlled and completely adaptive).
forward link: that portion of a Proximity space link in which the caller transmits and the
responder receives (typically a command link).
hailing: the persistent activity used to establish a Proximity link by a caller to a responder in
either full or half duplex. It does not apply to simplex operations.
hailing channel: the forward and return frequency pairs that a caller and responder use to
establish physical link communications.
physical channel: The RF channel upon which the stream of bits is transferred over a space
link in a single direction.
PLTU: The Proximity Link Transmission Unit is the data unit composed of the Attached
Synchronization Marker, the Version-3 Transfer Frame, and the attached Cyclic
Redundancy Check (CRC)-32.
CCSDS 211.1-B-3 Page 1-3 March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
Proximity link: short-range, bi-directional, fixed or mobile radio links, generally used to
communicate among probes, landers, rovers, orbiting constellations, and orbiting
relays. These links are characterized by short time delays, moderate (not weak)
signals, and short, independent sessions.
return link: that portion of a Proximity space link in which the responder transmits and the
caller receives (typically a telemetry link).
session: a continuous dialog between two communicating Proximity link transceivers. It
consists of three distinct operational phases: session establishment, data services, and
session termination.
space link: a communications link between transmitting and receiving entities, at least one of
which is in space.
synchronous channel: a data channel where the symbol data are continuously modulated
onto the channel at a fixed data rate. If the data link fails to provide frames (data or
fill), it is the responsibility of the physical layer to provide the continuous bit stream.
working channel: a forward and return frequency pair used for transferring User
data/information frames (U-frames) and Protocol/supervisory frames (P-frames)
during the data service and session termination phases.
1.5.2 NOMENCLATURE
The following conventions apply throughout this Recommendation:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
1.5.3 CONVENTIONS
In this document, the following convention is used to identify each bit in an N-bit field. The
first bit in the field to be transmitted (i.e., the most left justified when drawing a figure) is
defined to be ‘Bit 0’; the following bit is defined to be ‘Bit 1’ and so on up to ‘Bit N-1’.
When the field is used to express a binary value (such as a counter), the Most Significant Bit
(MSB) shall be the first transmitted bit of the field, i.e., ‘Bit 0’, as shown in figure 1-1.
CCSDS 211.1-B-3 Page 1-4 March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
BIT 0 BIT N-1

N-BIT DATA FIELD
FIRST BIT TRANSMITTED = MSB

Figure 1-1: Bit Numbering Convention
In accordance with standard data-communications practice, data fields are often grouped into
8-bit ‘words’ that conform to the above convention. Throughout this Recommendation, such
an 8-bit word is called an ‘octet’.
The numbering for octets within a data structure begins with zero. Octet zero is the first octet
to be transmitted.
By CCSDS convention, all ‘spare’ bits shall be permanently set to value ‘zero’.
Throughout this Recommendation, directive, parameter, variable, and signal names are
presented with all upper-case characters; data-field and MIB-parameter names are presented
with initial capitalization; values and state names are presented with predominantly lower-
case characters, and are italicized.
1.6 REFERENCES
The following documents contain provisions which, through reference in this text, constitute
provisions of this Recommendation. At the time of publication, the editions indicated were
valid. All documents are subject to revision, and users of this Recommendation are
encouraged to investigate the possibility of applying the most recent editions of the
documents indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS Recommendations.
[1] Information Technology—Open Systems Interconnection—Basic Reference Model: The
Basic Model. International Standard, ISO/IEC 7498-1. 2nd ed. Geneva: ISO, 1994.
[2] TM Synchronization and Channel Coding. Recommendation for Space Data System
Standards, CCSDS 131.0-B-1. Blue Book. Issue 1. CCSDS, September 2003.
[3] Proximity-1 Space Link Protocol—Coding and Synchronization Sublayer.
Recommendation for Space Data System Standards, CCSDS 211.2-B-1. Blue Book.
Issue 1. Washington, D.C.: CCSDS, April 2003.
[4] Proximity-1 Space Link Protocol—Data Link Layer. Recommendation for Space Data
System Standards, CCSDS 211.0-B-3. Blue Book. Issue 3. Washington, D.C.:
CCSDS, May 2004.
CCSDS 211.1-B-3 Page 1-5 March 2006
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ISO 21460:2007(E)
CCSDS RECOMMENDATION FOR PROXIMITY-1 SPACE LINK PROTOCOL—PHYSICAL LAYER
2 OVERVIEW
Proximity-1 is a bi-directional Space Link layer protocol to be used by space missions. It
consists of a Physical Layer (the subject of this document), a Coding and Synchronization
(C&S) sublayer (reference [3]) and a Data Link Layer (reference [4]). This protocol has been
designed to meet the requirements of space missions for efficient transfer of space data over
various types and characteristics of Proximity space links. On the send side, the Data Link
layer is responsible for providing data to be transmitted by the Coding and Synchronization
sublayer and Physical layer. The operation of the transmitter is state-driven. On the receive
side, the Data Link layer accepts the serial data output from the receiver (P
...